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United States Patent |
5,733,122
|
Gordon
|
March 31, 1998
|
Dental implant attachment assembly including device and method for
resisting loosening of attachment
Abstract
An attachment assembly for securing a dental prosthetic device to an
implant includes a post having a through bore which is adapted to be
secured in a recess in the prosthetic device, a primary fastening screw
having a head for engagement in the through bore and a threaded shaft for
projecting out of the through bore for threaded engagement in a
correspondingly threaded bore of an implant or implant abutment, and a
locking insert member for securing in the post through bore above the
primary screw with a lower end face of the insert member bearing against
the upper end face of the screw head in order to resist loosening of the
screw member once fastened to the implant.
Inventors:
|
Gordon; Basil (4 Gunnison, Irvine, CA 92715)
|
Appl. No.:
|
454601 |
Filed:
|
May 31, 1995 |
Current U.S. Class: |
433/172; 433/173 |
Intern'l Class: |
A61C 008/00 |
Field of Search: |
433/172,173,174,175,176
|
References Cited
U.S. Patent Documents
4631031 | Dec., 1986 | Richter | 433/173.
|
4713003 | Dec., 1987 | Symington et al. | 433/173.
|
4840529 | Jun., 1989 | Phillips | 411/397.
|
4850873 | Jul., 1989 | Lazzara et al. | 433/220.
|
4854873 | Aug., 1989 | Linden | 433/173.
|
5076788 | Dec., 1991 | Niznick | 433/174.
|
5106300 | Apr., 1992 | Voiik | 433/173.
|
5108288 | Apr., 1992 | Perry | 433/173.
|
5116225 | May., 1992 | Riera | 433/174.
|
5145371 | Sep., 1992 | Jorneus | 433/173.
|
5169308 | Dec., 1992 | Kvist | 433/172.
|
5180303 | Jan., 1993 | Hornberg et al. | 433/174.
|
5199873 | Apr., 1993 | Schulte et al. | 433/174.
|
5209666 | May., 1993 | Balfour et al. | 433/173.
|
5282746 | Feb., 1994 | Sellers et al. | 433/172.
|
5286195 | Feb., 1994 | Clostermann | 433/173.
|
5302125 | Apr., 1994 | Kownacki et al. | 433/172.
|
5342199 | Aug., 1994 | Gillespie | 433/173.
|
5350302 | Sep., 1994 | Marlin | 433/174.
|
5368480 | Nov., 1994 | Balfour et al. | 433/174.
|
5417569 | May., 1995 | Perisse | 433/174.
|
5439381 | Aug., 1995 | Cohen | 433/173.
|
Foreign Patent Documents |
473262 | Mar., 1992 | EP.
| |
61493 | Jan., 1994 | JP.
| |
Other References
Zest Anchors Pproduct Catalog.
|
Primary Examiner: O'Connor; Cary E.
Attorney, Agent or Firm: Brown, Martin, Haller & McClain
Claims
I claim:
1. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthesis, the post member having
an upper end, a lower end, and a through bore extending between the upper
and lower ends, the through bore having a step in diameter forming an
upwardly facing seating shoulder;
a fastening screw having a head seated in the through bore against the
seating shoulder and a threaded shaft projecting out of the through bore
through the lower end of the post member for releasable engagement in an
implant bore, the screw head having an upper face;
an insert member fitting in the through bore above the fastening screw, the
insert member having a lower end face facing the upper face of the screw
head for abutment with the upper face of the screw head;
the insert member having a locking mechanism for engaging the through bore
to releasably secure the insert member in a locking position in the
through bore in which the lower face of the insert member abuts against
the upper face of the screw head to resist loosening of the screw;
the upper face of the screw head having a recess for receiving a tool for
adjusting the tightness of the screw;
the insert member having a through bore for allowing access to the tool
receiving recess in the screw head;
the locking mechanism comprising a first fastener formation on the insert
member and the most member through bore having a second fastener formation
for mating engagement with the first fastener formation to secure the
insert member in the locking position; and
the fastener formations on the insert member and through bore comprising
mating screw threads, and the screw threads on the insert member being of
different dimensions to the screw threads on the screw shaft.
2. The assembly as claimed in claim 1, wherein the insert member
substantially fills the post through bore from the fastening screw up to
the upper end of the post member.
3. The assembly as claimed in claim 1, wherein the screw threads on the
insert member extend along at least part of the length of the insert
member from the lower end of the insert member.
4. The assembly as claimed in claim 3, wherein the screw threads extend for
at least 1.5 mm.
5. The assembly as claimed in claim 3, wherein the screw threads on the
screw shaft have a first depth and the screw threads on the insert member
have a second depth different from the first depth.
6. The assembly as claimed in claim 1, wherein the screw threads on the
insert member and through bore have a different pitch from the screw
threads on the screw shaft.
7. The assembly as claimed in claim 1, wherein:
the upper face of the screw head and the lower face of the insert member
have roughened surfaces.
8. The assembly as claimed in claim 1, wherein the upper face of the screw
head and the lower face of the insert member are ribbed surfaces.
9. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthesis, the post member having
an upper end, a lower end, and a through bore extending between the upper
and lower ends, the through bore having a step in diameter forming an
upwardly facing seating shoulder;
a fastening screw having a head for seating in the through bore against the
seating shoulder and a threaded shaft projecting out of the through bore
through the lower end of the post member for releasable engagement in an
implant bore, the screw head having an upper face;
an insert member for fitting in the through bore above the fastening screw,
the insert member having a lower face facing the upper face of the screw
head;
the insert member having a locking mechanism for engaging the through bore
to releasably secure the insert member in a locking position in the
through bore in which the lower face of the insert member abuts against
the upper face of the screw head to resist loosening of the screw;
the locking mechanism comprising a first fastener formation on the insert
member, and the through bore having a second fastener formation for mating
engagement with the first fastener formation to secure the insert member
in the locking position;
the first mating formations comprising a plurality of spaced, outwardly
projecting bayonet lugs on the lower end of the insert member; and
the second mating formations comprising a plurality of bayonet grooves
extending along the through bore for slidably receiving the respective
bayonet lugs, each bayonet groove having a lower end spaced above the
upper face of the screw head and a circumferentially extending bayonet
slot extending from the lower end for receiving the respective lug in a
rotated, locked position of the insert member.
10. The assembly as claimed in claim 9, wherein the bayonet slots are
inclined downwardly.
11. The assembly as claimed in claim 9, wherein the bayonet lugs have
downwardly inclined lower faces.
12. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthesis, the post member having
an upper end, a lower end, and a through bore extending between the upper
and lower ends, the through bore having a step in diameter forming an
upwardly facing seating shoulder;
a fastening screw having a head seated in the through bore against the
seating shoulder and a threaded shaft projecting out of the through bore
through the lower end of the post member for releasable engagement in an
implant bore, the screw head having an upper face;
an insert member for fitting in the through bore above the fastening screw,
the insert member having a lower face facing the upper face of the screw
head for abutment with the upper face of the screw head;
the insert member having a locking mechanism for engaging the through bore
to releasably secure the insert member in a locking position in the
through bore in which the lower face of the insert member abuts against
the upper face of the screw head to resist loosening of the screw;
the locking mechanism comprising a first fastener formation on the insert
member, and the through bore having a second fastener formation for mating
engagement with the first fastener formation to secure the insert member
in the locking position; and
the insert member having an outer surface facing the through bore, the
outer surface having at least one radially outwardly facing cut-out at a
location in its length, and the first mating formation comprising at least
one ball bearing slidably mounted in the cut-out for movement between a
retracted position in which the entire ball bearing is within the cut-out,
and an extended, locking position in which the ball bearing projects
partially out of the cut-out, and actuator means in the insert member for
urging the ball bearing outwardly into the locking position, and the
second mating formation comprising an annular groove in the through bore
for receiving the ball bearing in the extended position when the insert
member is in said locking position, whereby the insert member is
releasably secured in said through bore.
13. The assembly as claimed in claim 12, wherein said insert member has a
through bore intersecting said cut out, and an actuating member extending
through said bore for engaging said ball bearing, the actuating member
having a beveled end face comprising said actuator means, whereby the ball
bearing is urged outwardly as the actuating member is moved downwardly in
said bore.
14. The assembly as claimed in claim 12, wherein said actuator means
comprises a cam member for engaging said ball bearing.
15. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthesis, the post member having
an upper end, a lower end, and a through bore extending between the upper
and lower ends, the through bore having a step in diameter forming an
upwardly facing seating shoulder;
a fastening screw having a head seated in the through bore against the
seating shoulder and a threaded shaft projecting out of the through bore
through the lower end of the post member for releasable engagement in an
implant bore, the screw head having an upper face;
an insert member for fitting in the through bore above the fastening screw,
the insert member having a lower end face facing the upper face of the
screw head for abutment with the upper face of the screw head;
the insert member having a locking mechanism for engaging the through bore
to releasably secure the insert member in a locking position in the
through bore in which the lower face of the insert member abuts against
the upper face of the screw head to resist loosening of the screw;
the upper face of the screw head having a recess for receiving a tool for
adjusting the tightness of the screw;
the insert member having a through bore for allowing access to the tool
receiving recess in the screw head;
said insert member having an expandable outer sleeve and internal actuating
means for biassing said sleeve outwardly into an expanded position in
which said sleeve is in close frictional engagement with said through
bore, said expanded sleeve comprising said locking mechanism.
16. The assembly as claimed in claim 15, wherein said insert member
comprises two semi-cylindrical parts having opposing flat faces, said
sleeve comprising a resilient, C-shaped member enclosing said two parts to
retain them together, the flat faces of said parts having aligned recesses
forming an actuator bore, and an actuator member in said bore, said
actuator member being rotatable between an inoperative position and an
operative position in which said opposing parts are urged away from one
another to bias said sleeve outwardly into said expanded position.
17. The assembly as claimed in claim 16, wherein said actuator member
comprises a cam for bearing against the surface of at least one of said
recesses to urge said parts away from one another and expand said sleeve,
into said operative, locked position.
18. The assembly as claimed in claim 15 including a separate intermediate
joiner disc for locating between said insert member and screw head, the
screw head having a recess in its upper face, and the joiner disc having a
projecting boss shaped and dimensioned for mating engagement in said
recess.
19. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthesis, the post member having
an upper end, a lower end, and a through bore extending between the upper
and lower ends, the through bore having a step in diameter forming an
upwardly facing seating shoulder;
a fastening screw having a head for seating in the through bore against the
seating shoulder and a threaded shaft projecting out of the through bore
through the lower end of the post member for releasable engagement in an
implant bore, the screw head having an upper face;
an insert member for fitting in the through bore above the fastening screw,
the insert member having a lower face facing the upper face of the screw
head for abutment with the upper face of the screw head;
the insert member having a locking mechanism for engaging the through bore
to releasably secure the insert member in a locking position in the
through bore in which the lower face of the insert member abuts against
the upper face of the screw head to resist loosening of the screw;
the upper face of the screw head having a recess for receiving a tool for
adjusting tightness of the screw;
the insert member having a through bore for allowing access to the tool
receiving recess in the screw head; and
the insert member having an annular skirt depending downwardly from the
lower face for wedged engagement between the screw head and post member
bore.
20. The assembly as claimed in claim 19, wherein the skirt has a plurality
of slots around its periphery.
21. The assembly as claimed in claim 20, wherein the skirt is tapered
inwardly.
22. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthesis the post member having an
upper end, a lower end, and a through bore extending between the upper and
lower ends, the through bore having a step in diameter forming an upwardly
facing seating shoulder;
a fastening screw having a head seated in the through bore against the
seating shoulder and a threaded shaft projecting out of the through bore
through the lower end of the post member for releasable engagement in an
implant bore, the screw head having an upper face;
an insert member fitting in the through bore above the fastening screw, the
insert member having a lower end face facing the upper face of the screw
head for abutment with the upper face of the screw head;
the insert member having a locking mechanism for engaging the through bore
to releasably secure the insert member in a locking position in the
through bore in which the lower face of the insert member abuts against
the upper face of the screw head to resist loosening of the screw;
the upper face of the screw head having a recess for receiving a tool for
adjusting the tightness of the screw;
the insert member having a through bore for allowing access to the tool
receiving recess in the screw head;
the locking mechanism comprising a first fastener formation on the insert
member, and the through bore in the post member having a second fastener
formation for mating engagement with the first fastener formation to
secure the insert member in the locking position; and
the interchanging fastener formations on the insert member and post member
bore being coated with a resilient material.
23. A method of securing a prosthetic device to an implant via a primary
screw and resisting loosening of the primary screw, comprising the steps
of:
inserting a primary fastening screw having a head and a threaded shaft
through a bore in a post secured to a prosthetic device so that the
threaded shaft of the screw projects out through the end of the post;
using a tool engaging the head of the screw to tighten the threaded shaft
in a correspondingly threaded bore of an implant or implant abutment;
inserting a locking device into the through bore in the post above the
screw into a first position prior to a locking position in which the lower
end face of the locking device is in close frictional engagement with an
upper end face of the primary fastening screw to resist rotation of the
screw;
inserting the tool through a through bore in the locking device to engage
the head of the screw and tighten the screw further into the implant or
implant abutment until it reaches a fully engaged position in the implant
bore; and
securing the locking device in the locking position, whereby the locking
device resists loosening of the screw.
24. The method as claimed in claim 23, including the step of cutting the
locking device to a predetermined length corresponding to the length of
the post bore above the head of the fastening screw.
25. The method as claimed in claim 23, including the steps of cutting
threads in a portion of a prosthetic post through bore which match threads
on the outer surface of the locking device, and threading the locking
device into the threaded through bore portion into locking engagement with
the screw head.
26. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthetic device, the post member
having an upper end, a lower end, and a through bore extending between the
upper and lower ends, the through bore having a step in diameter forming
an upwardly facing seating shoulder;
a fastening screw having a threaded shaft for projecting out of the through
bore through the lower end of the post member for releasable engagement in
an implant bore and a retainer device positioned in the through bore and
engaging the seating shoulder to secure the prosthetic device to the
threaded shaft and implant;
an insert member fitting in the through bore above the retainer member;
the insert member having a locking mechanism for releasably securing the
insert member in a locking position in the through bore in which the
insert member abuts against the retainer device to resist loosening of the
screw; and
the fastening screw comprising a headless screw shaft and the retainer
device comprising a first nut threadably engaged on the screw shaft for
seating engagement on the seating shoulder when the shaft is threadably
secured in the implant bore.
27. The assembly as claimed in claim 26, wherein the insert member
comprises a second, lock nut for threaded engagement on the screw shaft
above the first nut, the lock nut having a lower face for frictional
engagement with the first nut to resist loosening of the screw.
28. An implant attachment locking assembly, comprising:
a post member for securing to a dental prosthetic device, the post member
having an upper end, a lower end, and a through bore extending between the
upper and lower ends, the through bore having a step in diameter forming
an upwardly facing seating shoulder;
a fastening screw having a threaded shaft for projecting out of the through
bore through the lower end of the post member for releasable engagement in
an implant bore and a head for engaging the seating shoulder and securing
the prosthetic device to the implant, the head having an upper face with a
threaded bore extending downwardly from the upper face; and
an insert member for fitting into the through bore above the fastening
screw, the insert member having a screw shaft for threaded engagement in
the threaded bore in the screw head, and a locking mechanism for
releasably securing the insert member against opposing portions of the
post member through bore to resist loosening of the screw.
29. The assembly as claimed in claim 28, wherein the post member through
bore has a tapered surface extending over a portion of its length spaced
from the upper end and from the seaming shoulder, and the insert member
has a tapered locking portion with a taper matching that of the tapered
surface of the through bore for close frictional engagement with the
tapered surface when the insert member is fully engaged with the threaded
bore in the screw head, the tapered locking portion and tapered surface
comprising said locking mechanism.
30. The assembly as claimed in claim 28, wherein the locking mechanism
comprises a split washer for fitting into the through bore above the
fastening screw, the split washer having a through bore with a tapered
inner surface, the insert member having a head with a tapered outer
surface for mating engagement with the tapered inner surface of the split
washer, whereby the split washer is urged outwardly into engagement with
the post member through bore to resist loosening of the screw.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to dental implant attachment
assemblies, and is particularly concerned with an implant attachment
assembly including a locking device for resisting loosening of a primary
fastening screw securing a prosthetic device to a dental implant.
Dental implants are surgically implanted in a patient's jawbone to provide
anchors for prosthetic devices such as crowns, bridges, dentures and the
like. Typically, the prosthetic device is secured to the implant by means
of a primary screw traversing the prosthetic device which engages the
female threading of the implant. A post is conventionally molded into the
prosthetic device during manufacture, the post having a through bore for
receiving the primary screw. The threaded shaft of the primary screw
projects out of the post and prosthetic superstructure for threaded
engagement in the implant bore. One problem with such arrangements is that
the primary fastening screw tends to loosen, rendering the attached
prosthesis unstable and loose.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new and improved
implant attachment assembly and method for resisting loosening of the
primary fastening screw of a dental implant arrangement.
According to one aspect of the present invention, an attachment assembly
for attaching to a dental implant is provided which comprises a post
member having an upper end, a lower end, and a through bore with a step in
diameter defining a seating shoulder, a fastening screw having a head for
seating in the through bore against the seating shoulder and a threaded
shaft for projecting out of the through bore through the lower end of the
post member for engagement in a matching threaded bore in an implant or
implant abutment. A locking insert member is provided for securing in the
through bore above the head of the fastening screw, the head of the
fastening screw having an upper face and the lower end of the insert
member having a lower face for engagement with the upper face of the
fastening screw when the insert member is secured in the through bore, and
a locking mechanism for releasably securing the insert member in the
through bore with the lower face of the insert member abutting the upper
face of the screw head.
Any suitable releasable locking mechanism may be provided between the
insert member and through bore. For example, the insert member and through
bore may be provided with interengageable screw threads along some or all
of their length. Alternatively, a bayonet locking mechanism may be
provided. In another embodiment, the insert member is expandable into
frictional locking engagement with the walls of the through bore. This has
the advantage that no modification to the existing bore or channel in a
post is needed, and the device can be retro-fitted to existing implant
secured prosthetic devices. In another alternative, the through bore may
be provided with a groove and ball bearings mounted in radial channels in
the insert member may be biassed partially into the groove to lock the
insert member in the desired position in which it bears against the upper
face of the fastening screw.
The insert member may be of softer material than the fastening screw, for
example a softer metal or a more resilient plastic material, so that it
can be compressed up against the upper face of the fastening screw head
and further resist rotation or loosening of the screw. The upper face of
the screw head and mating lower face of the insert member may each have
surface roughening, or alternatively may be ridged or grooved to increase
friction between the abutting surfaces and thus further resist loosening
of the screw.
The mating fastener formations may be mating screw threads of different
pitch from the threads on the fastener screw, or may be any other type of
locking formation such as bayonet lugs and grooves. The upper face of the
screw head typically has a recess shaped to receive the end of an
appropriate tool for tightening or loosening the screw, for example a
hex-shaped recess for receiving the end of a hex tool. Preferably, the
insert member has a through bore for access to the screw head by the tool
when the insert member is placed in the through bore. The through bore may
also be shaped for mating with the end of an appropriate tool for locking
the insert member in the through bore or releasing it when desired.
Alternatively, the insert member may have spaced peripheral cut outs at
its upper end for receiving an appropriate tightening tool.
Instead of providing a separate insert member, the head of the primary
screw may be elongated and provided with a locking surface mateable with
opposing portions of the post through bore.
According to another aspect of the present invention, a method of securing
a primary fastening screw in an implant to resist loosening of the screw
is provided, which comprises the steps of: inserting the fastening screw
into a bore in a post member with the threaded shaft of the screw
projecting out of the lower end of the post member, engaging the threaded
shaft in a correspondingly threaded bore of an implant, tightening the
screw until the head of the screw engages a seating shoulder in the post
member and the screw is secured to the implant, inserting a locking device
into the bore in the post member above the fastening screw, and engaging
fastener formations on the insert device with mating fastener formations
in the bore to secure the insert device in the bore and simultaneously
move the lower face of the locking device into abutment with the upper
face of the screw head, whereby the abutment between the opposing faces of
the locking device and screw head acts to resist any screw-loosening
rotation of the fastening screw.
As noted above, the insert or locking device preferably has a through bore
to permit access to a tool-receiving recess in the upper face of the screw
head while the insert is secured or positioned in the bore, so that the
screw can be tightened or loosened without first removing the insert. The
primary screw may be tightened first, and the insert or locking device may
then be tightened down into close abutment with the upper face of the
primary screw.
The implant attachment assembly of this invention allows the primary
fastening screw which secures a prosthetic device to an implant to be made
more secure against accidental loosening with use. The insert or locking
device is secured in close engagement with the upper face of the screw so
as to resist any movement of the screw, and thus resists loosening of the
screw.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be better understood from the following detailed
description of some preferred embodiments of the invention, taken in
conjunction with the accompanying drawings, in which like reference
numerals refer to like parts, and in which:
FIG. 1 illustrates a typical dental implant with an attachment assembly
according to one embodiment of the present invention securing a prosthetic
superstructure to the implant;
FIG. 2 is an enlarged sectional view taken on line 2--2 of FIG. 1;
FIG. 3 is a side view of the locking insert, showing an optional frictional
tip;
FIG. 4 is a bottom end view of the locking element, showing gripping
grooves;
FIG. 5 is a bottom end view showing surface roughening for frictional grip;
FIG. 6 is a sectional view similar to FIG. 2, showing an alternative twist
lock bayonet-type attachment of the locking insert;
FIG. 7 is a sectional view taken on line 7--7 of FIG. 6;
FIG. 8 is a side view of the lower end of the locking insert;
FIG. 9 is a view similar to FIG. 6, showing an alternative expanding
insert;
FIG. 10 is a sectional view taken on line 10--10 of FIG. 9, with the insert
in unlocked position;
FIG. 11 is a view similar to FIG. 10, with the insert in locked position;
FIG. 12 is a view similar to FIG. 9, with a wedge-type ball lock mechanism;
FIG. 13 is a sectional view taken on line 13--13 of FIG. 12;
FIG. 14 is a view similar to a portion of FIG. 12, with a cam actuated ball
lock mechanism;
FIG. 15 is a sectional view taken on line 15--15 of FIG. 14, with the ball
mechanism unlocked;
FIG. 16 is a similar sectional view with the ball mechanism unlocked;
FIG. 17 is a sectional view similar to FIG. 12 illustrating another
embodiment of the invention;
FIG. 18 is a sectional view similar to FIG. 17 illustrating another
modified embodiment;
FIG. 19 is a sectional view taken on line 19--19 of FIG. 18;
FIG. 20 is a sectional view similar to FIG. 17 illustrating another
modified attachment assembly and locking device; and
FIG. 21 is a sectional view similar to FIG. 20 illustrating a modification.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1-4 of the drawings illustrate an implant attachment assembly
according to a first embodiment of the present invention. The assembly is
used to attach a dental prosthetic device such as a crown, bridge or other
superstructure 10 to an implant 12 embedded and osseointegrated into jaw
bone 14. The assembly basically comprises a post or cylinder 16 having a
through bore 18, a primary fastening screw 20 seated in the lower end of
the bore 18 for securing the post 16 to implant 12, and a locking insert
or element 22 for securing in the bore above the screw 20 to resist
loosening of the screw.
Various types of dental implants are known which are designed to be
implanted in a prepared bore in the jawbone and which have a bore 24 for
attaching a superstructure to the implant directly or implant abutment
indirectly. Typically, the implant bore 24 is threaded for connection to a
fastening screw, although different types of implants have screw threads
of differing pitch, direction, and depth. The post or cylinder 16 has an
upper end 26 and a lower end 27 for abutment with the upper end of implant
12, or abutment where the tissue or gum 28 has a thickness above the
implant which is relatively small. Conventionally, where the gum is
relatively thick, a gingival collar or the like will be secured between
the implant and post 16, in which case the lower end of the post will
engage the upper end of the collar in a similar manner. The post is
designed to be embedded and secured in the dental prosthetic device or
superstructure 10 by an adhesive or the like, with the upper end of the
post exposed.
Through bore 18 extends between the upper and lower end of the post with a
step in diameter 30 adjacent the lower end which separates a larger
diameter, upper portion of the bore from the smaller diameter, lower end
of the bore. The primary fastening screw has a head 32 of diameter
slightly less than that of the larger diameter portion of bore 18, and a
smaller diameter, threaded shaft 34 with threads of dimensions matching
those of the implant bore 24, or a threaded bore in a gingival collar, if
used. The smaller diameter, lower end portion of bore 18 is of larger
diameter than the threads of shaft 34 so that the shaft may project freely
through the lower end portion of the bore. The step 30 forms a seat for
the head 32 of the shaft with the shaft projecting through the lower end
portion and out of the lower end of the post for threaded engagement in
implant bore 24, as best illustrated in FIG. 2. Head 32 has a conventional
recess 35 in upper face 36 for receiving the end of a suitable tool for
use in tightening the screw into the implant bore. The recess may be
hexagonal, for example, for receiving a hex driver tool.
Locking insert 22 is designed to fit into the upper end of the bore 18
above the screw so that it bears against the upper face of the screw to
resist loosening once the screw is secured in the implant bore. Suitable
interengageable mating formations are provided in the bore 18 and on the
outer surface of insert 22 for securing the insert in the bore. Insert 22
comprises a generally cylindrical member of diameter matching that of the
upper portion of bore 18 and having a lower face 38 for bearing against
the upper face 36 of the screw head. The insert 22 has a through bore 40
of diameter equal to or larger than that of the recess 35 at the upper end
of the screw head. Bore 40 may also be of hexagonal shape, as best
illustrated in FIG. 4, for engagement with an appropriate tool for
securing the insert in the bore 18.
The insert 22 has screw threads 42 on its outer cylindrical surface which
match the threads 43 on the inner surface of bore 18. The threads 42, 43
are of different dimensions to those on the shaft 34, for example of
different pitch, depth and/or orientation. Although the threads extend
along the entire length of the insert 22 as illustrated in FIGS. 2 and 3,
they may alternatively extend along only part of the length of the insert
from lower end 38. The threads must extend over a sufficient distance to
provide a sufficient locking force, and preferably extend for a length of
at least 1.5 mm. The remainder of the insert member may have a smooth,
cylindrical surface. Similarly, the threads 43 on the inner surface of
bore 18 may extend over only part of the length of the larger diameter
portion of the bore, and not up to the upper end 26 as in the illustrated
embodiment. If the insert 22 only has threads at the lower end for a
length of about 1.5 mm, the bore 18 will be threaded upwardly to the upper
end of the cylinder from a location just below the upper end 36 of screw
head 32.
The screw head 32 preferably has a bevelled upper edge 44, as illustrated
in FIG. 2. The insert member may have a reduced diameter, annular skirt 46
at its lower end which is designed to engage over the bevelled edge 44 as
illustrated in FIG. 2 with the lower end 38 in abutment with the upper end
face of the screw head. Preferably, some type of surface roughening or
other formations are provided on the upper end face 36 of the screw head
and the mating lower end face 38 of the locking insert, to ensure good
frictional contact between these faces. For example, as illustrated in
FIG. 4, the end faces may have alternating radial ribs 48 and grooves.
Alternatively, as illustrated in FIG. 5, the end faces may have surface
roughening 49 provided by sand blasting or the like. Any alternative types
of surface roughening, such as ridges, grooves, knurling or the like, may
be provided in order to produce good frictional contact between the faces
and to resist relative rotation between the parts when engaged.
The post 16, screw 20 and locking insert 22 may be of any suitable
material. The post and screw are preferably of a suitable metal for dental
use, and the insert 22 may be of the same material. However, the insert 22
is preferably of softer metal or other softer material than that of screw
20, so that it can be deformed into closer mating engagement with the
screw head.
In order to assemble the implant attachment as illustrated in FIG. 2, the
fastening screw is first inserted through bore 18 so that the projecting
end of shaft 34 engages in implant bore 24, using a suitable hex tool to
tighten the screw into the implant. When the screw is several turns away
from full engagement in bore 24, the locking insert is threaded into the
bore 18, using a similar hex tool of larger dimensions, until it is
several turns away from full engagement. The first screw is then tightened
down as far as it will go, and the insert 22 in turn is tightened down
until the lower end 38 is pressed into close frictional engagement with
the upper face 36 of screw 20.
In an alternative arrangement, the through bore 40 may have a lower end
portion of smaller dimensions matching those of recess 35, whereby the
same hex tool may be used to tighten both parts. The screw 20 is first
tightened until it is a few turns away from full engagement. The hex tool
is then engaged with the lower, smaller end portion of bore 40 and the
insert is tightened until it is two or three turns away from engagement.
The tool is then inserted through the insert 22 and into the recess 35,
and rotated to fully tighten the screw into the implant bore. The tool is
then retracted back into engagement with the appropriate portion of bore
40, and rotated to tighten down the locking insert on top of the screw.
With this arrangement, the locking insert bears down against the upper end
of the screw and resists any screw-loosening rotation due to the close
frictional engagement between the lower end face of the insert and the
upper end face of the screw. Because the threads of the locking insert are
of different pitch and have other differing parameters from those on the
screw, the two parts cannot loosen simultaneously.
The length and diameter of the locking insert will vary depending on the
type of implant system and superstructure with which it is to be used.
Different length locking inserts may be provided for different
superstructure applications, or the insert length may be custom cut or
adjusted at the upper end by the operator using standard dental
instrumentation. Inserts may also be provided in different diameters
depending on the diameter of the bore or channel in the post with which
they are to be used. Similarly, the diameter of the through bore 40 in
insert 22 will vary depending on the insert diameter as well as the
diameter of the tool-receiving recess at the upper end of the screw.
Generally, the insert will be provided in a range of lengths from 1.5 mm
to 15 mm.
Nylon or similar coatings may be applied to the fitting surfaces of the
primary fastening screw 20, the locking insert 22, and the threaded
surfaces of the post and implant, to reduce vibratory shock to the system
and also to reduce the ingress of saliva into the system. A locking washer
may also be provided under the head of the primary screw for providing
additional locking force to resist loosening.
FIGS. 6-8 illustrate an alternative embodiment in which a locking insert 50
is secured in a bore 52 of a post 54 by means of a bayonet connection
rather than screw threads. The locking insert 50 bears against a primary
fastening screw 20 which is identical to that of the previous embodiment,
and like reference numerals have been used for like parts as appropriate.
Screw 20 secures the post 54 to an implant 12 or a gingival collar in the
conventional manner, as discussed above.
In this embodiment, as in the first embodiment, the post 54 has a step 55
in diameter separating the larger diameter upper portion of the bore from
the lower end portion of the bore, through which the threaded shaft 34 of
screw 20 projects. The larger diameter portion of the bore has a series of
spaced, parallel grooves or channels 56 extending along its length from
the upper end 57 to a location which will be spaced just above the upper
surface 36 of the screw head. A downwardly inclined, transverse locking
slot 58 extends in a generally circumferential direction from the lower
end of each channel 56, with a detente at its lowermost end. In the
illustrated embodiment, three bayonet channels 56 are provided, although a
greater or lesser number may be provided if desired.
The locking insert 50 has three spaced bayonet lugs 60 projecting from its
outer surface adjacent the lower end 62 of the insert, for sliding
engagement along the bayonet channels 56 as the insert 50 is inserted into
bore. Preferably, the lugs 60 have a slight incline or ramped lower
surface. Once the lugs 60 reach the lower ends of the respective channels
56, the locking insert is rotated in a clockwise direction, so that the
lugs 60 travel along transverse slots 58 and, at the same time, the insert
is urged axially downwardly against the upper surface of the screw, due to
the incline of the slots 58 and the ramped lug surfaces. The insert is
rotated until each lug reaches the detente at the lower end of each slot
58, releasably locking the insert in the bore.
Optionally, the insert 50 has an annular skirt 64 projecting downwardly
from lower end 62 of the insert. Skirt 64 is inclined inwardly, as best
illustrated in FIG. 8, and has a plurality of castellations or slots 65
around its periphery. As the insert is forced downwardly against the upper
end face of the screw head 32, the skirt 64 engages the bevelled edge 44
of the screw head. This forces the skirt to expand resiliently outwardly
so that it is wedged between the edge of the screw and the wall of bore
52, further resisting any loosening of the screw 20.
As in the previous embodiment, the insert 50 has a hex-shaped through bore
66 aligned with the hexagonal recess on the upper face of the screw head.
Preferably, the insert also has a series of spaced, wrench-receiving slots
68 on its outer surface adjacent the upper end of the insert, as best
illustrated in FIG. 7. This allows a wrench-type tool to engage the slots
and turn the insert both to lock the bayonet lugs into the receiving slots
58, and to release the insert when desired- An annular plastic sealing
sleeve or ring 69 is mounted around the upper end portion of insert 50, as
illustrated in FIG. 6, to provide a saliva seal.
With this arrangement, the primary screw can be tightened into the implant.
The insert can conveniently be engaged in the bore simply by sliding it
vertically downwardly to the bottom of channels 56, and then turning
clockwise so that the lugs are forced down along slots 58. This will
simultaneously force the insert axially downwardly so that the lower end
face is urged into close frictional engagement with the upper face of the
screw head. Simultaneously, the skirt 64 is biassed outwardly by the
bevelled rim of the screw head and is jammed between the screw head and
cylindrical bore. As in the previous embodiment, the upper face of the
screw head and abutting lower face of the insert will have suitable
surface formations for increased frictional engagement, such as ribs,
bumps, knurls or other surface roughening.
When the locking insert is locked in position, any loosening of the screw
will be resisted by the engagement of the lower end face of the insert
with the screw head. This significantly reduces the risk of the screw
becoming loose over time.
FIGS. 9-11 illustrate another alternative embodiment of the invention in
which an insert member 70 can be retro-fitted to an existing implant
attachment assembly without requiring any modification of the channel or
bore 72 in post member 73. The insert member 70 of FIGS. 9-11 comprises
two semi-cylindrical halves 74, 75 which have at least partially
semi-circular recesses 76, 77 on their mating flat faces which together
define a through bore through the insert member. The two halves 74, 75 may
optionally be held in a C-shaped metal sleeve or sheath 79. Sleeve 79 may
be made with different wall thicknesses so that the insert member can be
fitted in different diameter channels 72.
One of the recesses 77 has an eccentric cut-out 80, as best illustrated in
FIGS. 10 and 11, and has screw threads for threaded engagement with
central actuating screw 81. Screw 81 has a tool-engaging recess 82 at its
upper end for engagement with a suitable tightening tool such as a hex
driver. Screw 81 has a projecting cam surface 83 which is located in the
cut-out 80 when the screw is in an inoperative position, as illustrated in
FIG. 10. As in the previous embodiments, the lower end faces of the two
halves 74, 75 may have suitable surface roughening or projections for
close frictional engagement with the upper end face of fastener screw 84
which secures the assembly to an implant in the same manner as in the
previous embodiments. Additionally, because different manufacturers of
fastening screws have differently machined hex tool recesses, an
intermediate mating joiner 110 is used where the lower side specifically
engages the hex recess and its upper side engages the insert, thereby
providing a male/female torque-locking mechanism. Joiner 110 has a
projecting hex boss 112 for mating engagement in hex bore 114 at the upper
end of screw 84, as illustrated in FIG. 9. Cylindrical projection 115 at
the lower end of the insert halves 74, 75 engages in a corresponding
recess 116 at the upper end of joiner 110. Joiners will be provided with
differently machined hex bosses for mating with all conventional fastening
screws.
In order to install the insert member, the device is pushed axially
downwardly into channel 72 until the lower end face engages the upper end
face of screw 84. Screw 81 is then rotated in a clockwise direction,
causing cam surface 83 to move out of cut out 80 and urge the insert
halves 74, 75 apart, expanding the effective diameter of the insert, as
illustrated in FIG. 11. The outer surface of the expanded sleeve 79 will
bear against the inner surface of channel 72, and the frictional
engagement between the two surfaces will hold the insert member in the
channel. Preferably, the sleeve 79 is of copper or other suitable
material.
Rather than using a cover to expand the two halves 74, 75, a tapered screw
may be used, such that as the screw is screwed into the bore formed by
recesses 76, 77, the gradually increasing diameter of the screw will urge
the two halves apart.
FIGS. 12 and 13 illustrate another alternative insert member 85 and
wedge-type ball locking mechanism 86 for securing the insert member in
channel 87 and against the upper end face of primary fastener screw 20. In
this embodiment, the channel 87 is provided with an annular groove 88
adjacent the upper end face 36 of screw 20. Insert member 85 has a single
or a pair of oppositely directed radial cut-outs or channels 89 adjacent
its lower end face and a ball bearing 90 is located in each channel 89. A
through bore 91 extends through insert member 85 to intersect the inner
ends of cut outs 89. Bore 91 has screw threads at least adjacent its lower
end. A secondary screw member 93 having a beveled lower end portion 94
extends through bore 91. Screw member 93 has threads 92 adjacent beveled
end portion 94 for threaded engagement with the threads in bore 91. A tool
receiving recess 96 is provided in the upper end of screw member 93.
In order to secure the insert member 85 in bore or channel 87, it is
slidably inserted into the channel until the lower end face engages the
upper end face of the primary screw 84. As in the previous embodiments,
the mating end faces may have suitable surface roughening, ribs, grooves
or the like for enhanced frictional engagement. At this point the screw 93
is rotated clockwise, moving downwardly such that the beveled portion 94
urges the ball bearings 90 outwardly into groove 88, forcing the insert
member downwardly into close mating engagement with the upper end face of
the screw 84, and locking the insert member in the channel. Thus, the
insert member will resist any loosening of primary screw 84.
FIGS. 14-16 illustrate a modification which is similar to the embodiment of
FIGS. 12 and 13 in that a ball lock mechanism is used, in which ball
bearings 90 engage in grooves 88 to lock insert member 85 in position, and
like reference numerals have been used for like parts as appropriate.
However, a cam actuated mechanism is used for urging ball bearings 90
outwardly in this embodiment. Thus, rather than a screw member with a
tapered or beveled end portion for urging the ball bearings outwardly, a
screw member 97 in threaded bore 91 is secured to a cam member 98 mounted
in through bore 91 in alignment with ball bearings 90. In the inoperative
position of FIGS. 14 and 15, the ball bearings are in their retracted
position. Once the insert member 85 is inserted to a position in which the
ball bearings are aligned with groove 88, the screw member 97 is rotated
one quarter turn, from the position of FIG. 15 to that of FIG. 16. The cam
bears against the ball bearings and forces them outwardly to engage in
groove 88, locking the insert member in the channel with the lower end
face bearing against the upper end face of the primary screw 84 to resist
rotation. A detente mechanism 118 is incorporated in the opposite end
faces of the cam to prevent it from unintentionally unlocking.
Although the embodiments of FIGS. 12-16 each use two ball bearings, a
single ball bearing may alternatively be used, or a greater number of ball
bearings may be used if necessary. In all of the above embodiments, the
insert member is releasably locked in the channel of a denture post so as
to bear against a primary fastener screw securing the post and denture to
an implant or implant abutment, and resist loosening of the primary screw.
Other possible techniques for locking the insert in the bore include a
lever mechanism, a gate device or a projection which extends through the
side wall of the insert. These devices may be reversibly activated.
FIG. 17 of the drawings illustrates an implant attachment assembly and
locking device according to another embodiment of the invention. In this
embodiment, post or cylinder 120 has a through bore 122 of stepped
diameter with shoulder or seat 124, and a headless fastener screw 125
comprising an elongate, threaded shaft projects through the bore 122 for
threaded engagement in the threaded bore 24 of implant 12. A hex bore 126
is provided in the upper end of screw 125 for receiving a suitable tool
for tightening the screw in bore 24. Rather than having an integral head
as in the previous embodiments, the screw 125 in this version has a
primary fastening nut 127 tightened on the threaded shaft. The nut 127
engages seat 124 when the screw 125 is tightened in bore 24. A second,
locking nut 128 is then tightened onto the shaft and tightened down so
that its lower surface is in close, frictional engagement with the upper
surface of the first nut 127, resisting loosening of the assembly. The
opposing faces of the two nuts may have roughened surfaces or the like, as
described above in connection with FIGS. 4 and 5.
FIGS. 18 and 19 illustrate another alternative attachment assembly and
locking device which can be retro-fitted into an existing post without any
modification to the post bore. In this embodiment, post 130 is secured to
implant 12 by means of a primary fastening screw having a head 132 and
threaded shaft 134 for threaded engagement in the implant bore. Post 130
has a through bore with a step or seat 135 as in the previous embodiments,
against which the head 132 is seated when the primary screw is secured in
the implant bore.
The locking device in this embodiment comprises a partially split washer
137 having a downwardly tapering, conical through bore 138, and a locking
screw 139 having a conical head 140 for mating engagement in the washer
bore 138, and a threaded shaft 141 for threaded engagement in a
correspondingly threaded portion 142 of a bore in the upper face of the
primary screw. The washer is split along at least part of its length, as
illustrated in FIG. 19. The washer bore 138 and screw head 140 have a
matching taper of between 6.degree. and 20.degree. The primary screw bore
has a threaded upper end portion 142, and a hex portion 144 at its lower
end for engagement with a suitable screw tightening tool.
In order to install this assembly, the primary screw is first inserted into
the post bore and a suitable hex tool is engaged in hex portion 144 in
order to tighten the shaft 134 into the implant bore and tighten head 132
against seat 135. The washer 137 and locking screw combination is then
inserted into the bore above the head 132 of the primary screw. Head 140
has a hex bore 145 at its upper end for receiving the end of a suitable
tool for tightening shaft 141 into the upper threaded portion 142 of the
primary screw bore. As the locking screw is tightened down into the bore
in the primary screw head, it will simultaneously bear against the split
part of washer 137, urging the two halves apart and into close mating
engagement with the surface of the post bore, while the lower end face of
washer 137 is also urged downwardly into close mating engagement with the
upper face of screw head 132. The frictional engagement between these
surfaces will help to resist loosening of the primary fastening screw. The
washer 137 may be of any suitable material such as metal or more resilient
material.
FIG. 20 illustrates another modified embodiment in which post 148 has a
through bore 149 having a downwardly tapered, frusto-conical portion 150
leading from a larger diameter portion of the bore to a smaller diameter
portion 151. A step or seat 152 is provided at the lower end of bore
portion 151 leading to the smallest diameter, lower end portion 153 of the
bore. The primary fastening screw has an elongated head 154 of diameter
substantially matching that of the intermediate bore portion 151, and a
shaft 155 having screw threads for threaded engagement in the implant
bore, as in the previous embodiment, with head 154 seated against step
152. A locking insert 156 having a frusto-conical surface 157 of taper
matching that of the tapered portion 150 of the post bore is jammed into
the bore above the head 154 of the fastening screw. Insert 156 has a
threaded shaft 158 for threaded engagement in an upper, threaded portion
159 of a bore in the upper face of the screw head. The lower end of the
bore comprises a hex portion 160 for receiving a suitable hex tool. The
upper end face of insert 156 also has a hex bore or recess 162.
In order to secure the post 148 to an implant 12, the primary fastening
screw is inserted through the post bore and the shaft is screwed into the
threaded implant bore until the head is closely seated against shoulder
152. The screw is tightened by means of a suitable hex tool engaging in
the hex-shaped lower end portion 160 of the bore in the screw head. Once
the screw has been securely fastened, the tool is removed and the insert
156 is placed into the bore above the fastening screw, with shaft 158
threaded into the threaded portion 159 of the screw head bore by means of
a hex tool engaging in hex bore 162 to tighten the insert down until the
mating tapered surfaces 150 and 157 are in close engagement. The implant
member is compressed against the tapered surface 150 and forms a cold weld
with that surface, locking the parts together and resisting loosening of
the primary fastening screw.
FIG. 21 illustrates a modification of the previous embodiment, in which a
tapered surface 170 is provided on the head 172 of the primary fastening
screw, and the separate insert member is eliminated. Instead, the head of
the primary fastening screw has been modified to perform the function of
the insert 156 of the previous embodiment. In this embodiment, the post
174 has a bore with an upper portion 175 of a first diameter, a tapered
portion 176 with a taper matching that of the tapered surface 170 of the
screw, and a lower end portion 177 of reduced diameter. The screw head 172
has an upper portion 178 of diameter matching that of the upper portion
175 of the post bore, and a threaded shaft 180 projecting downwardly from
the tapered surface 170 through bore portion 177 for threaded engagement
in the bore of implant 12. The tolerance between the screw head 172 and
the inner diameter of the bore in post 174 is very tight. Screw head 172
has a hex-shaped bore or receptacle 182 at its upper end for receiving a
suitable tool for tightening the screw in the post. The upper end portion
178 of the screw head 172 may be extended up to fill the entire post bore
if desired, and the length of portion 178 may be adjusted as necessary
depending on the height of the post.
The fastening screw is inserted into the post so that the threaded shaft
projects out of the lower bore portion 177. A suitable tool is engaged in
hex bore 182 and the screw is tightened into the threaded bore of implant
12. Simultaneously, the tapered surface 170 is pushed against the matching
portion 176 of the bore, pushing outward against the tapered portion 176
and creating frictional engagement between the screw head and post bore.
An effective cold weld is formed between the tapered surfaces, thus
resisting loosening of the fastening screw.
In each of the embodiments of FIGS. 18-21, the taper of the opposing
tapered surfaces is between 6.degree. and 20.degree.. This allows a cold
weld to be formed between the opposing surfaces, resisting loosening or
backing out of the primary screw. FIGS. 20 and 21 illustrate how a
separate insert member can be eliminated and the head of the primary screw
can be modified to perform the same function as the separate insert
member. Some of the previous embodiments can be modified in an equivalent
manner to provide the locking function on the screw head instead of a
separate insert member, for example the embodiments of FIGS. 9-16.
However, the first two embodiments require a separate insert member.
The locking inserts of the above embodiments will all resist loosening of
the primary fastening screw attaching a prosthetic dental device to an
implant. Thus, the risk of such prosthetic devices becoming loose,
unstable and uncomfortable is significantly reduced. Another advantage of
the insert arrangement is that the insert will fill the space in the post
above the fastening screw, preventing or reducing the risk of saliva
ingress and potential bacterial contamination. The insert arrangement is
compatible with all existing implant devices.
Although some preferred embodiments of the invention have been described
above by way of example only, it will be understood by those skilled in
the field that modifications may be made to the disclosed embodiments
without departing from the scope of the invention, which is defined by the
appended claims.
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